1. Field of the Invention
The invention relates to flow meters for measuring flow volumes, particularly in a flow of gas such as in pulmonary function diagnoses, wherein a flow resistance comprises a mechanical-electrical transducer disposed in a flow tube.
2. The Prior Art
Flow meters are known wherein the drop in pressure across a flow resistance is measured by a differential pressure-sensitive device connected by lines into opposite interior spaces of a flow tube divided by the resistance element. The flow resistance is a fine-meshed wire net. Such flow meter is complex since it is constructed into two parts.
A one-piece flow meter is shown in U.S. Pat. No. 2,989,866, comprising a wire resistance strain gage incorporated in the flow resistance element. Although differential pressure is measured, the wire strain gage complicates flow meter construction, is somewhat unreliable, and provides more resistance to flow of air in one direction than in the other flow direction through the tube.